Tuesday, March 4, 2014

Three pisicale method are used for determined deference in elevations. Normally barometric leveling, trinometric leveling, and sprit leveling.

1.Barometric leveling

Barometric leveling mark use of the pinerminon that deference in elevation between 2 points is proportional to the difference in atmostiric pressures at the point. A barrow meter there for heavy used and the readings observed at difference points world yield a measure of the relative elevations of those points at a given points. The atmospiaric pressures duos not reaming constant in the course of the even in the course of in hours of the even in the course of hours. There for relatively inaccurate an is little used in surveying work except on reconnaissance for expio rotator surveys.

2.Trigonometric leveling (indirect leveling)

This I s the cross of leveling In which the elevations of points are computed from the vertical angles and horizontal distance measure in the field just as the length of any side in any triangle can be computed from proper trigonometric relations in the modified from called stadia leveling. Commonly using in mapping broth of the difference of elevations and the horizontal distance between the points are directly computed from the measure vertical angle and staff readings.

3.Sprit leveling(direct leveling )

It is that branch of leveling in witch the vertical distances witch respect to a horizontal line(perpendicular to the directions of gravity). May be used to determined the relative deference in elevations 2 between adjacent points. a horizontal plane of site tangent to level surface at any point is reading establish by means of a sprit level and a sighting devise(telescope) are combined and vertical distance are measure by observing on graduated rods rise on the point. The method is also known as direly leveling. It is the most precise method of ditumiding elevations and the one most commonly used by engineers.